Separation of mixtures of hydrocarbons



Patented Jan. 30, 1940 [UNITED STATES SEPARATION OF MIXTURE 0F] HYDROCARBONS j Melvin A. Dietrich, Wilmingtom Del., ,assi gnonto E. I. du Pont de Nemours &, Company, Wibv mington, Del., 2. corporation ofDelaWare.' No Drawing. Application May 19.1936,

Serial No. '80,55 6

I 10 Claims. (01.1196513'Jj. j

This invention relates to the separation of mix tures of hydrocarbons by selective solvent action and more particularly tothe solvent refining of mineral oils.

It is now well known thata large proportion of,

the mineral-oilsand gasolines of today arecomplex mixtures of parafiinic and non-paraffinic hydrocarbons, It is frequently desirable to separate the non-parafiinic hydrocarbons from. the paramnic hydrocarbons for various'reasons. One of the main reasons is that the parafiinic hydrocarbons are in general more resistant to ecomposition through heat and oxidation than.

the non-parafnnic hydrocarbons. Accordingly.

.the oil containing the larger proportion of parafiinic constituents or, in other words, the relatively more parafiinic oils are more stable tl'ran' and non-paraffinic hydrocarbons into portions,

one of which is relatively more paraflinic than the original mixture andthe other relativelyjless paraffinic. Another object is the separation of relatively non-paraffinic, bodies from mineral luricating oils to produce lubricating oils of. rela-" tively.v high parafiinic character. A further object is theproduction of, lubricating. oils, with improved viscosity-temperature curves from oils with poor viscosity-temperature curves A still further object is to provide oils with improved 7 resistance to oxidation and decompositionand to advance the art. Still other objects will appear hereinafter. ,v

These objects 'may' be accomplished inQaccordance with my invention by treating mixtures of paraffinic and non-parafiinic hydrocarbonswith I a iuronitrile to remove the non-parafiinic hydrocarbons by the selective action of the furonitrile.

By the term afuronitrile1 mean furonitrile (C4H'3OCN) and its homologues such as the methyl and ethyl furonitriles.

, The o'il is mixedwith the furonitrileunder such conditions that two layers are formed, one ofwhich comprises the constituents which it is de- -.sired to extract from the oil, dissolved in the bulk of the liquid solvent, while the other comprises the undissolved and relatively. parafiinic oil in admixture with a relatively small amount,

of the solvent. Preferably, my method comprises mixing the furonitrile with the hydrocarbon mixmixed'with an equal volume of furonitrile, heated.

ture inapproxi'matelyequal volumes. and .heating TAO-Fries, 1

withagitation to atemperature at which the sblventtandoil becorne=-:subs tantially completely miscibl'es -This solution isth'en cooled with agitatio-n to a temperatureapproximately 20 C. be-

low the temperature of complete miscibility, al-

lowing themixturetostand until separation into 1 two layers occurs,- separating the layers and removing thefur'onitr'ile from each layer;- The-110 carbons by distillation. Theresidue, from the layer containing the larger. amount of solvent",

furonitrile vmaybe separated from the hydroconsists of alarge proportion of non-paraffinici and undesirable constituents. -The-residue, from;

the layer containing the smaller amountofasolvent; consists primarily of the desirable paraf finicihydrocarbons. p

1 In". the examples given below thepselectlveremoval of; non-parafiinic constituents from a mineral'oil; has been measured by following the change in viscosity-gravityconstant of the oil;

and-by determining the'change inviscosity index. The viscosityegravity constant and its determination has been described-byJ. B. Hill andH. .B. Coates in Industrial and Engineering Chemistry.

vol. 20, page 641, et,-seq., in an article. entitled The 'Vis'cosityeGravity Constant of Petroleum Fractions: of. a, parafiinic characterhave; lower constantsthan fractions of Lubricating Oils.

a naphthenic character. Viscosity index and its calculation llasibeen describedby Dean and Davis in Chemical; and Metallurgical Engineering, vol.\

36, page 618. This index serves as a'measure -of the flatness of the viscosity-temperature curve of an oil. Highvalues .of;th'eE index. are shown by oilswhich-areQprimariIyparaffinic in character.

A- lubricating 011 distillate- (with the following characteristics: "viscosity at F., 566. sec. Saybolt Universal; specific gravity at 60 JFK/60f F. viscosity-gravity constant, 0.872) was with agitation to 40 .C. at which temperature solvent and oil were miscible.fi- The solution was cooled to =10 ,C., while agitating, allowed to settle one-half hour, and the two layers withdrawn into separate, containers. QFurOnitriIe was removed from'both layers under reduced pressure; The

top layer was found to contain69-% of the volume of the original oil. This oil had the following characteristics:..viscosity.at 100-F., 435 sec.-;- at

index. 67: 1

Example 2 y i .The lubricating distillate was treated as in Example 1 with the exception that the separation temperature was 20 C. Oil recovered from the 210 F'.,.55.5, sec;specific gravity at 60FL/609 0.9053; viscosity gravity constant, 0.844; viscosity 55 top layerwas 64% of the volume of the original oil and possessed the following characteristics: viscosity at 100 F., 422 'sec.; at 210 F., 55 sec.;

specific gravity at 60 F./60 R, 0.9029; viscosity: H

mixture to separate into two layers, separating gravity constant, 0.843; viscosity index, 6'7.

The conditions of application .of the solvent will vary with the nature 'of the oil.

' At the higher temperatures, it may be necessary to employ pressure to prevent substantial va'p'ortzation of the solvent. The ratio of solvent to,oil.. may be varied within rather wide limits and will depend largely vupon-'the-nature. of the oil being treated, the amount .of non-paraflinic constituents :therein and the quality of the refined oil desired. In"general,ithe ratio of solvent'to oil will lie between 1 to 10 and 5 to 1 parts by volume.

The application of the furonitriles as selective solvents is not confined to lubricating oil dis-' tillates. They may be employed to refine other hydrocarbon or mineral oil .fractions such as cracked naphthas, gasoline, or kerosene fractions,

whose boiling ranges are sufficiently different from "the-solvent to 1 permitseparation of the furonitrile. not be pure but "may beincluded in mixtures, particularly mixtures of other solvents. Extraction treatment withthe furonitrile may be applied to a raw distillate or to apartially' refined product. Under certain coriditioris'for example in the case of oils with high sulfur content or poor s'ludging characteristics it may be desirable 'to supplement the furonitrileextraction with the usual acid, alkali, doctor, or clay treatment applied either before or after the solvent extraction.

While I have disclosed the preferred embodim'ents of my invention and the preferred modes of carrying 'the'sa'me into eifect, it will be readily apparent to those skilled in the'art that'many variations and modifications may be made thereinfwithout departing from the spirit of my invention. Accordingly, the scope of my invention is to be limited solely by the appendedclaims construed as broadly'as is permissible in view of the priorart,

1. The method, of treating a I normally liquid hydrocarbon mixture containing relatively paraffinic and relatively, non-paraflinic compounds which comprises extracting the hydrocarbon mixture with afuronitrile to "separate the relatively non paraflinic compounds from therelatively parafiinic compounds.

2. The method of treating anormally liquid hydrocarbon mixture containing relativelyparaffinic and relatively non-parafiinic compounds which comprises mixing a furonit rile with the hydrocarbon mixture, causing the resulting mixture to separate into two layers andseparating the, layers whereby the relatively non-paraffinic compounds, are separated from the relatively -pa'raflinic compounds; v

3. The method offtjreating a normally liquid hydrocarbon mixture containing relatively paraffinic and relatively non-paraffii'iic compounds Which comprises mixing a furonitrile with the hydrocarbon mixture, heating the resulting mixvHighly naphthenic oils will, in general, require a lower temperature to effect separation than I highly parafiinic oils. The temperatures employed will, ingeneral, range from about 0 C. to'about200 C.

The furonitrile as employed need ture to a temperature where the furdnitrile becomes completely miscible with the hydrocarbon mixture, cooling to about 20 C. below the temerature of complete miscibility and causing the the two layers, and removing the furonitrile from ".eachklayer, whereby the relatively non-parafiinic compounds are separated from the relatively parafiinic compounds.

7 ,4. The method of treating a normally liquid hydrocarbon mixture containing relatively paraf- -finic and relatively non-parafiinic compounds which "comprises extracting the hydrocarbon mixture with furonitrile to separate the relatively non-paraffu'iic compounds from the relatively par'aftinic compounds.

ture to separate into two layers and separating the layers, whereby the relatively non-parafrinic compounds are separated from the relatively paraffinic compounds.

6. The method of treating a normally liquid.v hydrocarbon mixture containing relatively paraffinic and relatively non-parafiinic compounds which comprises mixing furonitrile with the hydrocarbon mixture, heating the resulting mixture'to a temperature where the furonitrile becomes completely miscible with the hydrocarbon mixture, cooling to about 20 C. below the temperature of complete miscibility and causing the mixture to separate into two layers, separating the two layers, and removing the furonitrile from each layer, whereby the relatively nonparafiini'c compounds are separated from the relatively paraffinic compounds.

'7. The method .of refining mineral oil containing naphthenic and parafilnic constituents to separate the oil into fractions respectively rich in these. constituents comprising mixing the oil with pyro-muconitrile, forming an extract phase containing naphthenic constituents dissolved in the solvent and, a rafiinate phase comprising relatively parafiinic constituents of the oil, separating the two phases, and removing the solvent liquid therefrom.

into

9, Themethod' of treating a normally liquid finic and relatively non parafiinic compounds which comprises extracting the hydrocarbon mixture with ethylfuronitrile toseparate the relatively non-parafiinic compounds from the relatively paraffinic compounds.

MELVIN A. DIETRICH. 

